Oh, EVERYONE should have a Hot Stone Massage at some time! They're wonderful

You can have a massage even when you are full term lying down if your massage therapist has the pregnancy mats that go on the table and accommodate the pregnant belly.

You shouldn't have a massage in the first trimester, esspecially if you are at high risk for miscarriage, but other than that it should be fine.

I massage pregnant women and its never been a problem before, the other option is to have a seated massage where you are propped up with pillows under your tummy and breast while you sit on a chair backwards. Its very comfortable this way too.